Immune Response Of Nile Tilapia Research Articles

The role of HMGB2 in the immune response of Nile tilapia (Oreochromis niloticus) to streptococcal infection

High mobility group protein B2 (HMGB2) is an abundant chromatin-associated protein with pivotal roles in transcription, cell proliferation, differentiation, inflammation, and tumorigenesis. However, its immune function in Nile tilapia (Oreochromis niloticus) remains unclear. In this study, we identified a homologue of HMGB2 from Nile tilapia (On-HMGB2) and investigated its functions in the immune response against streptococcus infection. The open reading frame (ORF) of On-HMGB2 spans 642 bp, encoding 213 amino acids, and contains two conserved HMG domains. On-HMGB2 shares over 80 % homology with other fish species and 74%–76 % homology with mammals. On-HMGB2 was widely distributed in various tissues, with its highest transcript levels in the liver and the lowest in the intestine. Knockdown of On-HMGB2 promoted the inflammatory response in Nile tilapia, increased the bacterial load in the tissues, and led to elevated mortality in Nile tilapia following Streptococcus agalactiae infection. Taken together, On-HMGB2 significantly influences the immune system of Nile tilapia in response to streptococcus infection.

High stocking density affected the growth performance, digestive enzyme activity, intestinal histology, and immune response of Nile tilapia (Oreochromis niloticus) fry grown in brackish water

High stocking density affected the growth performance, digestive enzyme activity, intestinal histology, and immune response of Nile tilapia (<i>Oreochromis niloticus</i>) fry grown in brackish water

Dietary algal-sourced zinc nanoparticles promote growth performance, intestinal integrity, and immune response of Nile tilapia (Oreochromis niloticus)

BackgroundTrace elements play a crucial role in fish nutrition, with zinc (Zn) being one of the most important elements. BIO-sourced zinc nanoparticles were synthesized using the green microalga Pediastrum boryanum (BIO-ZnNPs, 29.35 nm). 30 or 60 mg/ kg dry feed of the BIO-ZnNPs (BIO-ZnNPs30 and BIO-ZnNPs60) were mixed with the Nile tilapia (Oreochromis niloticus) basal diet and fed to the fish for 8 weeks to evaluate their impact on fish growth, digestion, intestinal integrity, antioxidative status, and immunity.ResultsA significant enhancement was observed in all investigated parameters, except for the serum protein profile. BIO-ZnNPs at 60 mg/kg feed elevated the activities of reduced glutathione (GSH) and catalase (CAT), enzymatic antioxidants, but did not induce oxidative stress as reflected by no change in MDA level. Fish intestinal immunity was improved in a dose-dependent manner, in terms of improved morphometry and a higher count of acid mucin-producing goblet cells. Interleukin-8 (IL-8) was upregulated in BIO-ZnNPs30 compared to BIO-ZnNPs60 and control fish groups, while no significant expressions were noted in tumor necrosis factor-alpha (TNFα), nuclear factor kappa B (NFkB), and Caspase3 genes.ConclusionOverall, BIO-ZnNPs inclusion at 60 mg/kg feed showed the most advantage in different scenarios, compared to BIO-ZnNPs at 30 mg/kg feed. The positive effects on growth and intestinal health suggest that BIO-ZnNPs supplementation of aquafeeds has many benefits for farmed fish.

Assessing the impact of two forms of PACAP-38 (pituitary adenylate cyclase-activating polypeptide) on Nile tilapia (Oreochromis niloticus) immune response following challenge with Flavobacterium columnare

Antimicrobial peptides have been isolated from various organisms and play an essential role in defense against infections. They are small peptides (less than 60 amino acids) with broad-spectrum antibacterial activity. In teleosts, pituitary adenylate cyclase-activating polypeptide (PACAP) has been demonstrated to have direct antimicrobial activity against several aquatic pathogens, including those from the genus Flavobacterium. Our goal was to examine the impacts of PACAP and route of administration on the immune response of Nile tilapia (Oreochromis niloticus). Over the course of four studies, tilapia (416.1 ± 116.7 g) randomly assigned to replicate tanks were administered with either PACAP-38 or a modified form of PACAP-38 via intraperitoneal (i.p.) injection, bath, nares flush, or gill flush, and compared to PBS controls. In the first two studies, following individual treatments, tilapia underwent a bath exposure (40 L tank for 45 min) to F. columnare (isolate ALG-00-530; at 2.1 × 108 CFU/ml) or sham exposure without the addition of the bacterial culture. Fish were sampled before exposure, 48 h after stimulation, at 1 day after the onset of mortality in exposed tanks, and resolution of mortality. Tilapia that received i.p. injection of PACAP-38 showed significantly lower mortality from F. columnare (10 %) than those receiving PBS i.p. (25 %). However, bath immersion of fish, both with and without F. columnare, resulted in significant mortality due to secondary infections with Edwardsiella tarda. Administration of modified PACAP-38 via nares/gill flush, or i.p. injection did not, however, result in significantly fewer mortalities compared to sham/PBS. Furthermore, the same modified form of PACAP-38 also induced inflammatory gene expression in the spleen, and eosinophilic granule cell aggregation in the nares, following flushing. The data from the first study suggest that PACAP-38 induces protection against infection and stress mainly through a reduction of inflammatory-il1β expression. Moreover, data analysis of spleen samples from these two studies also indicates that PACAP-38 might have more anti-inflammatory impacts than its modified form. In the fourth trial, after exposing tilapia to low temperature (15–17 °C) for 30 min (cold stress), the PACAP-38 treated group had significantly lower cortisol levels compared to both PBS injected group and the negative control. Due to the observed impacts of PACAP-38 treatment on the immunophysiology of Nile tilapia, its potential for therapeutic use should be further investigated.

Duration of Protection and Humoral Immune Response in Nile Tilapia (Oreochromis niloticus L.) Vaccinated against Streptococcus agalactiae.

Streptococcosis caused by Streptococcus agalactiae (S. agalactiae) is a major bacterial disease affecting the production of Nile tilapia (Oreochromis niloticus L.), causing significant economic losses due to mortality in the growing phase. Vaccination is the most effective method for preventing streptococcosis on Nile tilapia farms. In Brazil, the major tilapia-producing regions have long production cycles (6-10 months) and harvest tilapias weighing over 900 g for fillet production. Thus, data on the duration of the humoral immune response and protection in farmed tilapia have not been reported or are poorly described. Furthermore, the efficiency of serological testing for the long-term monitoring of immune responses induced by vaccination against S. agalactiae has never been addressed. This study evaluated the duration of protection and humoral immune response induced in Nile tilapia vaccinated against S. agalactiae until 300 days post-vaccination (dpv). The immunization trial was composed of two groups: vaccinated (Vac), vaccinated intraperitoneally with a commercial vaccine, and unvaccinated (NonVac) group, injected fish with sterile saline solution. At 15, 30, 150, 180, 210, and 300 dpv, blood sampling was conducted to detect anti-S. agalactiae IgM antibodies using indirect Enzyme-Linked Immunosorbent Assay (ELISA), and the fish were challenged with pathogenic S. agalactiae to determine the duration of vaccine protection through relative percentage survival (RPS). Spearman's rank correlation was performed between the ELISA optical density (OD) of vaccinated tilapia and the duration of vaccine protection (RPS). The mean cumulative mortality in NonVac and Vac groups ranged from 65 to 90% and less than 35%, respectively. The average RPS was 71, 93, 94, 70, 86, and 67% at 15, 30, 150, 180, 210, and 300 dpv, respectively. RPS revealed that the vaccine provided protection from 15 to 300 dpv. The specific anti-S. agalactiae IgM antibody levels were significantly higher in the Vac group than that non-Vac group up to 180 dpv. The vaccinated fish exhibited significant protection for up to 10 months after vaccination. There was a positive correlation between the antibody response and RPS. This study revealed that a single dose of commercial vaccine administered to Nile tilapia can confer long-term protection against S. agalactiae and that indirect ELISA can monitor the duration of the humoral immune response for up to six months following vaccination. Finally, vaccine protection over six months can be associated with other components of the fish immune system beyond the humoral immune response by IgM antibodies.

Toxicity and therapeutical impacts of Bee venom (Apis mellifera L.) on Nile tilapia juvenile (Oreochromisniloticus)

Bee venom (BV) has been widely studied for its therapeutic properties in various medical applications. However, its effects on aquatic organisms, particularly Nile tilapia (Oreochromis niloticus), remain poorly understood, particularly concerning toxicity and therapeutic impacts. This study investigated the effects of bee venom (BV) injection on Nile tilapia (O. niloticus) by examining growth, feed efficiency, biometric parameters, whole-body chemical analysis, and the activity of antioxidant enzymes in the liver. Nile tilapia juveniles were injected with BV at doses of 0, 3, 6, 9, and 12 mg/kg of fish weight. Observations were made on the 14th day post-injection (DPI). No significant differences were found in growth, feed utilization, survival rate, biometric indices, and whole-body composition among the BV dosage groups. Similarly, the activity of intestinal enzymes (amylase, protease, and lipase) showed no significant changes. However, the study revealed a time-dependent response of antioxidant enzymes (SOD, CAT, and GPx) in the liver, with activity peaks on the 4th and 6th DPI. On the 14th DPI, fish injected with BV at doses of 3, 6, and 9 mg/kg exhibited higher antioxidant enzyme activities compared to the control and the highest dosage group (12 mg/kg). These results imply the presence of potential adaptive antioxidant activity and a favorable influence on the health and immune responses of Nile tilapia following BV injection. Notably, the effects appear to vary with the dose, influencing both antioxidant enzyme activities and immunity. Further research is warranted to explore the long-term effects of BV exposure and its potential therapeutic applications in aquaculture.

Expression profiles of four Nile Tilapia innate immune genes during early stages of Aeromonas veronii infection.

During Egypt's hot summer season, Aeromonas veronii infection causes catastrophic mortality on Nile Tilapia Oreochromis niloticus farms. Egypt is ranked first in aquaculture production in Africa, sixth in aquaculture production worldwide, and third in global tilapia production. This study aimed to investigate, at the molecular level, the early innate immune responses of Nile Tilapia to experimental A. veronii infection. The relative gene expression, co-expression clustering, and correlation of four selected immune genes were studied by quantitative real-time polymerase chain reaction in four organs (spleen, liver, gills, and intestine) for up to 72 h after a waterborne A. veronii challenge. The four genes studied were nucleotide-binding oligomerization domain 1 (NOD1), lipopolysaccharide-binding protein (LBP), natural killer-lysin (NKL), and interleukin-1 beta (IL-1β). The four genes showed significant transcriptional upregulation in response to infection. At 72 h postchallenge, the highest NOD1 and IL-1β expression levels were recorded in the spleen, whereas the highest LBP and NKL expression levels were found in the gills. Pairwise distances of the data points and the hierarchical relationship showed that NOD1 clustered with IL-1β, whereas LBP clustered with NKL; both genes within each cluster showed a significant positive expression correlation. Tissue clustering indicated that the responses of only the gill and intestine exhibited a significant positive correlation. The results suggest that NOD1, LBP, NKL, and IL-1β genes play pivotal roles in the early innate immune response of Nile Tilapia to A. veronii infection, and the postinfection expression profile trends of these genes imply tissue-/organ-specific responses and synchronized co-regulation.

Dietary propolis improves the growth performance, redox status, and immune response of Nile tilapia upon a cold-stress challenge.

The purpose of this research was to demonstrate the potential of adding propolis (PR) to the diet of Nile tilapia (Oreochromis niloticus) to mitigate the harmful effect of cold stress (CS) on the growth performance, redox status, and immunological response. Two trials were conducted in this study. First, 210 Nile tilapia fingerlings (28.61±0.20 g) were used in a preliminary trial to determine the appropriate PR level and supplementation period to be applied for the main trial. Fish were assigned into 7 treatment groups (3 aquaria replicates × 10 fish per aquarium in each treatment group) according to the rate of PR supplementation in the fish diets at 0, 2, 4, 6, 8, 10, and 12 g/kg for 6 consecutive weeks. The average body weight and body weight gain were determined weekly. It was found that PR supplementation at 10 g/kg in fish diet for 4 weeks was enough to obtain significant results on the growth performance of Nile tilapia. For the main trial of the present study, 480 Nile tilapia fingerlings (average weight 29.93±0.11 g) were distributed into randomized 2 PR × 2 CS factorial treatment groups (6 replicate aquariums containing 20 fish in each group). Fish of PR groups received a basal diet for a feeding period of 4 weeks, included with 10 g/kg PR (+ PR group) or without PR inclusion (- PR group). Fish of the CS groups were either challenged with cold stress at 18°C (+ CS group) or maintained at a temperature of 26°C during the feeding period (- CS group). The results showed that CS challenge significantly (p < 0.05) impaired the growth indices, redox status, and immune response in the challenged fish compared to the non-challenged fish. On contradictory, the inclusion of PR into fish diets enhanced (p < 0.05) the feed intake, growth indices, antioxidant enzyme activity, and immunological parameters. Moreover, PR treatment alleviated the CS deterioration of fish weights, specific growth rates, feed efficiency, antioxidant enzyme activity, lymphocyte proliferation, and phagocytosis activity and alleviated the elevated mortality, H/L ratio, and malondialdehyde levels by cold stress. It is concluded that the inclusion of propolis at 10 g/kg in the diet of Nile tilapia fish could be approved as a nutritional approach to enhance their performance, especially when stressed by low-temperature conditions.

Efficacy of an Insect-Based Diet with Addition of Probiotics on Growth, Proximate Composition, Enzymatic Efficiency, and Immune Response of Nile Tilapia

Insects are potential alternative protein sources to replace fish meal (FM) in aqua feed. The role of insect species as replacements in the aqua industry has been a hot debate in the current era. The present study evaluated the influence of FM replacement with insect-based meals (black soldier fly (BSF) and maggot fly) in the feed of Nile tilapia. Eight diets with graded replacement levels of FM were formulated along with basal diet as T0 (control group having basal diet), T1 (25% maggot meal (MM) with 2% probiotics), T2 (50% MM + 2% probiotics), T3 (75% MM + 2% probiotics), T4 (100% MM + 2% probiotics), T5 (25% BSF meal (BSFM) + 2% probiotics), T6 (50% BSFM + 2% probiotics), T7 (75% BSFM + 2% probiotics), and T8 (100% BSFM + 2% probiotics). Fish having an initial body weight of 7 g were fed on formulated feed for 16 weeks. Growth parameters, including weight, length, feed conversion ratio, specific growth rate, and survival rate, were observed weekly, and significant ( p &lt; 0.05 ) results were attained up to 75% replacement level with no adverse effect on growth. However, at 100% replacement of FM, fish growth was retarded. Maximum survival rate was observed in T1 and T5 and minimal in T4 and T8. Body composition, including crude protein, fat, moisture, and ash, showed significant ( p &lt; 0.05 ) results. Similarly, digestive enzyme (protease, lipase, and amylase) activity was measured at the end of the trial. Fish in T1 and T5 groups had the highest digestive enzyme activity, which slightly decreased with the inclusion of insect-based meals and probiotics. Statistically significant ( p &lt; 0.05 ) results were observed for antioxidant enzyme activity in catalase, glutathione peroxidase, and superoxide dismutase. The most vigorous immune response was shown in T1 and T5, with higher white blood cells and high levels of IgM. The present research showed that FM could be replaced with BSF meal and MM with probiotics up to 50% for better fish health performance; however, 75% replaced FM without compromising growth and health status.

Effect of Dayak Onion (Eleutherine bulbosa (Mill.) Urb.) on the Immune Response and Gene Expression of Nile Tilapia (Oreochromis niloticus) Infected with Aeromonas hydrophila

Abstract Dayak onion (Eleutherine bulbosa (Mill.) Urb.) has the potential to be an immunostimulant to benefit fish health. This study aimed to evaluate the effectiveness of dietary supplementation with the powder and crude ethanol extracts of Dayak onion on the hematology and immune response parameters of Nile tilapia challenged with Aeromonas hydrophila. The research used a completely randomized design with six treatments and three replications. Nile tilapias were fed with Dayak onion (w/v) consisting of powders of 5% (P5), 10% (P10), and 15% (P15), while crude extract was 0.5% (E05) and given during rearing for 30 days. Positive control (C+) and negative control (C-) were used without Dayak onion. Nile tilapia in treatment C+, P5, P10, and P15 were injected with A. hydrophila 10⁶ CFU mL⁻1, while that in treatment C- was injected with phosphate buffered saline (PBS) intramuscularly. The results showed that the dietary with 15% powder and 0.5% crude extract significantly improved the hematology and immune response parameters compared to the control after the challenge against A. hydrophila (P&lt;0.05). Dayak onion supplementation effectively increased the health status based on hematology and immune response parameters of Nile tilapia against A. hydrophila infection. Highlight Research Dayak onion has significant potential to improve nonspecific immunity in fish. Dayak onion improves hematology and immune response of Nile tilapia. Dayak onion can significantly regulate the immune system against A. hydrophila infection. Dayak onion significantly increases the production of the gene expression of IL-1β and TNF-α.

Effect of Bacillus Probiotics on the Immunological Responses of Nile Tilapia (Oreochromis niloticus): A Review

The use of antibiotics and therapeutics for Nile tilapia has increased along with its increased production and intensification. Probiotics have been studied as an alternative to the excessive use of antibiotics in fish diets. Studies have demonstrated that dietary Bacillus probiotic inclusion promotes faster growth and disease resistance in farmed fish species. Despite advances in research, there is still uncertainty about the mechanisms controlling the immune response of fish. In this review, we summarize and discuss recent research on the immune responses of Nile tilapia to Bacillus probiotics. Through the use of immunological information including phagocytosis, lysozyme activity, respiratory activity, antioxidant proteins, complement activity, and immune-related gene expression, researchers hope to develop effective strategies for successfully using Bacillus probiotics in Oreochromis niloticus farming.

Molecular characterization and functional analysis of CD209E from Nile Tilapia (Oreochromis Niloticus) involved in immune response to bacterial infection

CD209 plays significant roles in pathogen recognition, innate and adaptive immunity, and cell-cell interactions. In the present study, a CD209 antigen-like protein E from Nile tilapia (Oreochromis niloticus) (designated as OnCD209E) was identified and characterized. OnCD209E contains an open reading frame (ORF) of 771 bp encoding a 257 amino acid protein, as well as the carbohydrate recognition domain (CRD). Multiple sequence analysis exhibits that the amino acid sequence of OnCD209E was relatively high homologous to that of partial fish, especially the highly conserved CRD, in which four conserved disulfide-bonded cysteine residues, WIGL conserved motif and two Ca2+/carbohydrate-binding sites (EPD and WFD motifs) were founded. Quantitative real-time PCR and Western Blot revealed that OnCD209E mRNA/protein is generally expressed in all tissues examined, but with wealth in head kidney and spleen tissues. The mRNA expression of OnCD209E was significantly increased in brain, head kidney, intestine, liver, and spleen tissues in response to the stimulation with polyinosinic-polycytidylic acid, Streptococcus agalactiae and Aeromonas hydrophila in vitro. Recombinant OnCD209E protein exhibited detectable bacterial binding and agglutination activity against different bacteria as well as inhibited the proliferation of tested bacteria. Subcellular localization analysis revealed that OnCD209E was mostly localized in the cell membrane. Moreover, overexpression of OnCD209E could activate nuclear factor-kappa B reporter genes in HEK-293T cells. Collectively, these results demonstrated that CD209E may potentially involve in immune response of Nile tilapia against bacterial infection.

Partial dietary fishmeal replacement with mixture of plant protein sources supplemented with exogenous enzymes modify growth performance, digestibility, intestinal morphology, haemato-biochemical and immune responses for Nile tilapia, Oreochromis niloticus

For the aquaculture sector, expanding the amount of plant proteins substituting fish meal (FM) is favorable. This study was conducted to evaluate the properties of diets containing a blend of plant protein sources (cotton seed meal, sunflower meal and jojoba (CSJ)) instead of FM and supplemented with a mixture of exogenous enzymes on the growth performance, intestinal morphology, blood indices, activity of endogenous and digestibility also, immune response of Nile tilapia, Oreochromis niloticus. Three groups of the experimental diet (29.5% crude protein) and (18.76 MJ kg −1 gross energy) were performed. The first group CSJ1 was (FM: CSJ = 2:1), the second group diet CSJ2 was (FM: CSM = 2:2) and the third CSJ3 was (FM: CSJ = 2:1), the replaced was based on content of protein. All groups of diets were supplemented with mixture of enzymes (Protease, pepsin, trypsin, xylanase and amylase) at 0 and 0.5 g kg −1 diet therefore six diet was formulated. Fingerlings (6.30 ± 0.09 g) were randomly allocated into eighteen plastic tank (450 L capacity) in triplicate per each treatment (25 fish/ treatment) for 90 days. After 90-days of the feeding trial, results indicated that the highest wight gain and best FCR, higher (P < 0.05) activity of trypsin and lipase, apparent digestibility coefficient of nutrients were detected in fish fed diet of FM: CSJ 2:1 and 2:2 supplemented with 0.5 g enzymes mixture kg−1 diet with insignificant differences between group. The diet incorporating FM: CSJ 2:1 with 0.5 g enzymes mixture showed the maximum (P < 0.05) villi length/width, ASA, and MSR values. Fish fed a diet containing FM: CSJ 1:2, and supplemented with 0.5 g of an enzyme mixture kg−1 diet had the maximum Hb, Htc, RBCs and WBCs values (P < 0.05). The highest (P < 0.05) TP and GL value was estimated in diet containing FM: CSJ; 1:2 without the addition of enzymes mixture. while, the best (P < 0.05) value of ALT and AST were showed in diet containing FM: CSJ 2:1 without the addition of enzymes. The highest TAC, GSH and SOD values were recorded by fish fed diet containing FM: CSJ 1:2 or 2:2 with 0.5 g enzymes mixture kg−1 diet. Fish fed diets comprising various ratios of FM: CSJ with 0.5 g enzymes mixture kg−1 diet had the lowest (P < 0.05) MDA value. In conclusion, using mixture of enzymes (protease, pepsin, trypsin, xylanase and amylase) at 0.5 g kg−1 in combination with a high blend of CSJ instead of FM; 2:2 improved the growth performance, digestibility, digestive enzyme, intestinal morphology, blood indices, and immune response of Nile tilapia.

Molecular characterization and immune functions of lipasin in Nile tilapia (Oreochromis niloticus): Involvement in the regulation of tumor necrosis factor-α secretion

Lipasin, the product of the angiopoietin-like 8 (angptl8) gene, is known as a critical regulator of plasma lipid metabolism. However, its immune function in vertebrates is currently poorly understood. By 5'/3′-rapid amplification of cDNA ends (RACE), we established the structural identity of Nile tilapia (Oreochromis niloticus) angptl8. The transcripts of tilapia angptl8 were widely expressed in various tissues, with the highest levels in the liver. Following lipopolysaccharide in vivo challenges, time-dependent angptl8 gene expression was observed in the head kidney and liver. On the basis of the sequence obtained, we produced recombinant lipasin that inhibited lipoprotein lipase activity. Treatment of head kidney leukocytes with lipasin stimulated tumor necrosis factor-α (TNF-α) secretion and gene expression. In addition, lipasin-induced TNF-α secretion could be prevented by inhibiting the nuclear factor-kappa B (NF-κB) signaling pathway. Furthermore, lipasin enhanced the phosphorylation and degradation of IκBα and promoted translocation of the p65 subunit of NF-κB to the nucleus. Collectively, the current findings suggested that lipasin was involved in the immune response of Nile tilapia and stimulated TNF-α secretion by activating the NF-κB pathway in tilapia head kidney leukocytes.

Characterization of CD166 from Nile tilapia (Oreochromis niloticus) displays a broad pathogen recognition spectrum and involved the immune response to microbial aggression

CD166 is a member of the immunoglobulin superfamily of cell adhesion molecules, and its mediated adhesion plays a crucial role in different physiological and pathological phenomena, especially related to leukocyte extravasation, immune synapse stability, T cell activation and proliferation. In this study, CD166 was identified from Nile tilapia (Oreochromis niloticus, OnCD166). OnCD166 contains an open reading frame of 1671 bp that encodes a peptide of 556 amino acids, and contains five consecutive extracellular immunoglobulin domains. It's tissue distribution and expression patterns after S. agalactiae challenge were also investigated. OnCD166 is widely distributed in various tissues of healthy tilapia. After Streptococcus agalactiae challenge, OnCD166 expressions were significantly up-regulated in all tested immune tissues. Meanwhile, the recombinant OnCD166 (rOnCD166E) protein showed strong agglutinating activities against both Gram-negative bacteria and Gram-positive bacteria. Moreover, rOnCD166E could promote phagocytosis of macrophages. Taken together, our results illustrated that OnCD166 might as a receptor involved in the immune recognition and phagocytosis against invading pathogen, which play important roles in the immune responses of Nile tilapia against bacterial pathogens.

Early innate immune responses of Nile tilapia (Oreochromis niloticus) during tilapia lake virus (TiLV) infection

Tilapia lake virus (TiLV) poses a serious threat to global tilapia aquaculture industry, causing massive mortality and huge economic losses. In the present study, we describe an experimental challenge of Nile tilapia using tilapia lake virus with emphasis on the expression profile of immune genes IPS-1 and TLR-7. Healthy Oreochromis niloticus (Nile tilapia) fingerlings were intraperitoneally injected with 50 μl of 1×105 TCID50/ml of TiLV prepared by growing the virus in EPC cells. Infection was followed with histopathology and gene expression analysis in the main target organs viz. brain, liver and kidney at 12, 24, 48, 72 and 96 h post challenge (hpc). Microscopic examination revealed localized blood clotting in the brain cortex, syncytial cell formation and presence of putative intracytoplasmic inclusion bodies in the liver tissue. Innate immune gene expression of IPS-1 was down regulated in the liver while slightly upregulated in kidney and brain during the early infection period. The innate sensor, TLR-7 showed downregulation in liver and upregulation in the brain, which was also evident by the very little pathology noticed in the brain. Overall, the lack of upregulation of innate immune genes in immunocompetent tissue like kidney could be due to increased multiplication of the virus in these tissues by interfering in the immune signalling pathway.

Thymomodulin enhances vaccination responses against Streptococcus agalactiae in Nile tilapia

Streptococcosis caused by Streptococcus agalactiae is a major economic problem for Nile tilapia Oreochromis niloticus production worldwide. Inactivated vaccines are considered an efficient method for controlling streptococcosis. However, during the vaccination process, stress during fish handling could affect the immune response. Immunomodulators, such as thymomodulin, act on the immune system and can improve vaccination responses. Thus, the aim of this study was to assess the immunomodulatory effect of thymomodulin in O. niloticus vaccinated against S. agalactiae. For this, fish were distributed in a factorial design (2x2x6), corresponding to two levels of thymomodulin supplementation (0.0 and 0.3%), two treatments (sterile phosphate buffered saline and inactivated S. agalactiae vaccine). Initially, fish received thymomodulin supplementation for 30 days. Next, fish were vaccinated by injection intraperitoneal (i.p.) of heat inactivated S. agalactiae vaccine. 15 days after vaccination, all fish were challenged i.p. with S. agalactiae and blood samples were collected at 7, 14, 21 days post infection (DPI). Results revealed that fish supplemented with thymomodulin vaccinated or not developed better protection against S. agalactiae than vaccinated fish without thymomodulin. Furthermore, fish vaccinated and supplemented with thymomodulin presented high levels of antibodies after 14 and 21 DPI, suggesting that thymomodulin can promote the immune response in Nile tilapia.

Functional characterization of complement factor H in host defense against bacterial pathogen in Nile tilapia (Oreochromis niloticus)

Complement factor H (CFH), a multifunctional soluble complement regulatory protein, can bind to a variety of pathogens and play a crucial role in host innate immune defense. To explore the functional characteristics of CFH (OnCFH) in Nile tilapia (Oreochromis niloticus), we cloned and characterized the open reading frame (ORF) of OnCFH in this study. The full-length of OnCFH ORF is 1359 bp, encoding 452 aa for a 48.85 kDa peptide, and its predicted structure containing six short complement-like repeats (SCRs). The analysis of tissue distribution showed that OnCFH was constitutively expressed in all tested tissues, with the highest in the liver. Upon Streptococcus agalactiae and Aeromonas hydrophila stimuli in vivo and in vitro, OnCFH mRNA transcript was significantly upregulated in head kidney tissue as well as head kidney monocytes/macrophages. Further, the recombinant OnCFH protein ((r)OnCFH) could bind to pathogenic bacteria in a dose-dependent. Moreover, it got involved in the regulation of inflammation as well as phagocytosis of monocytes/macrophages. The knockdown of OnCFH remarkably decreased the amount of bacteria in the head kidney. In summary, our data demonstrated that OnCFH could participate in the immune response of Nile tilapia against bacterial infection.

Activated T cells are the cellular source of IL-22 that enhances proliferation and survival of lymphocytes in Nile tilapia

As a pleiotropic cytokine mainly secreted by CD4+ T cells, interleukin (IL)-22 plays an important role in immune regulation and infection elimination. Despite IL-22 homologues have been identified in non-mammal, whether and how IL-22 participates in the adaptive immune response of early vertebrates have not been fully addressed. In this study, we identified an evolutionarily conserved IL-22 from Nile tilapia Oreochromis niloticus (defined as OnIL-22), proved by its properties regarding sequence, gene structure, functional domain, tertiary structure and phylogeny. IL-22 was broadly expressed in lymphoid-related tissues of tilapia, and with relatively higher levels in skin, gill, intestine and liver. The expression of OnIL-22 in spleen lymphocytes was markedly induced at the adaptive immune stage after Streptococcus agalactiae infection. Moreover, once lymphocytes were activated by PMA plus ionomycin or T-cell specific mitogen PHA in vitro, OnIL-22 expression was obviously up-regulated at both mRNA and protein levels. These results thus suggest that activated T cells produce IL-22 to take part in the adaptive immune response of tilapia. Furthermore, treatment of lymphocytes with recombinant OnIL-22 increased the expression of genes related to proliferation and survival, and further promoted the proliferation and reduced the apoptosis of lymphocytes during bacterial infection or T-cell activation. These cellular effects of IL-22 seem to be associated with JAK1/STAT3 axis downstream of IL-22, because IL-22 application not only elevated the mRNA expression of JAK1 and STAT3, but also enhanced their phosphorylation in lymphocytes. Altogether, we suggest that activated T cells produce IL-22 to promote lymphocyte proliferation and survival probability via JAK1/STAT3 signaling pathway, thus participating in adaptive immune response of Nile tilapia. Our study therefore provides helpful perspective for understanding the function and mechanism of adaptive immune system in teleost.

Administration of some probiotic strains in the rearing water enhances the water quality, performance, body chemical analysis, antioxidant and immune responses of Nile tilapia, Oreochromis niloticus

The performance, efficiency of consumed feed, body chemical composition, survival rate, antioxidant and immunity parameters of Nile tilapia (Oreochromis niloticus) reared in probiotic-treated water were studied. Two hundred apparently healthy Nile tilapia (20 ± 0.3 g) juveniles were reared for 70 days in five different treatments, with five replications as the control group (clean water) and four test groups with two probiotics strains (Bacillus toyonensis and Geobacillus stearothermophilus) at two different levels (1 or 2 × 105 CFU ml−1) applied in rearing water. Fish reared in water supplemented with G. stearothermophilus at low level demonstrated significantly enhanced (p < 0.05) growth performances in terms of final body weight (FBW), weight gain (WG), daily weight gain (DWG), specific growth rate (SGR), and relative growth rate (RGR) compared to the control group. In the same context, supplied fish rearing water a lower amount of G. stearothermophilus (GS1) remarkedly reduced feed conversion ratio values when compared to the control group. In contrary, all other feed efficiency parameters increased significantly when G. stearothermophilus (GS1) water was added at low amount in the compartment with the untreated group. Moreover, probiotic water additives significantly reduced the range and median levels of unionized ammonia (NH3) in water when compared to the untreated group. According to the findings of the body chemical composition, treated tilapia water with a high level of B. toyonensis had significantly higher crude protein and fat levels, as well as lower ash levels, than the control group. When compared to the control group, probiotic-water supplementation significantly improved oxidative status and immunological activity at all bacterial dosage levels, with the fish group enriched with a high level of G. stearothermophilus recording the maximum values of both antioxidant and immune activity. Finally, results reveal that water treated with B. toyonensis or G. stearothermophilus as a probiotic promoted Nile tilapia growth and health status, and this technology may be applied to stimulate tilapia productivity in culture farms.